Access of virtual machines to storage area networks

ABSTRACT

A method for managing access of virtual machines executed by a host computer system to storage area networks, the storage area networks connecting the host computer system with storage systems via switches, where the host computer system includes one or more host ports to connect with a switch each, and where one or more port names are assigned to each virtual machine. The method includes, for each storage area network connected with the host computer system, sending the port names of a virtual machine and a target port name as part of a validate access command to the respective switch; and when receiving the validate access command by the switch, the switch returning success information to the sending host computer system in case all received virtual machine port names have access to a target port assigned to the received target port name, otherwise returning a fail information.

BACKGROUND

Aspects of the present disclosure relate to data processing systems, andin particular, to a method, system and computer program product formanaging access of virtual machines executed by a host computer systemto storage area networks.

Many commercial and other enterprises use storage area networks (SANs)for distributing, acquiring, and managing vast quantities of data. A SANis a network in which one or more host servers access one or morestorage units such as hard disks, optical disks, and tape drives.Typically, each host server includes one or more host-bus adapters(HBAs), each with one or more physical ports.

Large SANs tend to employ virtualization on many levels to allowflexible configuration and reconfiguration of hardware resources.Virtual servers or virtual machines can be used so that a single servercan emulate several smaller servers, each with its own instance of anoperating system. Disk arrays are divided into logical units (LUNs) thatcan service different host adapter ports (from the same or differentphysical servers). Multiple virtual HBA ports can be assigned to aphysical port and used so that different virtual servers (running on thesame server) can have exclusive access to different sets of LUNs usingthat same physical HBA port.

Operating Systems access fiber channel storage through world-wide uniqueidentifiers (WWPNs) or identifiers (FC_IDs) tied to a plug position on aFiber Channel (FC) switch. FC networks typically implement Zoning andLUN masking, which restrict access between WWPNs and FC_IDs fromany-to-any to a number of administrator-defined sets. When OperatingSystem instances, such as virtual machines, are moved from one server toanother server they still need access to their original data, using aset of unchanged IDs (in the WWPN case) or changed IDs (in the SwitchPort case).

When virtual servers using storage area network (SAN) attached storageare to be flexibly deployed and moved around on physical servers (nodes)of a server cluster or cloud, using particular port names to access theSANs and storage resources on storage controllers, it generally must beensured that port names with identical SAN and storage accesscapabilities are available for use by the virtual servers on any of thenodes on which they are supposed to run, and can be associated with anyof the host ports they are supposed to use on any of these nodes.

SUMMARY

Embodiments of the present disclosure provide for a method, system, andcomputer program product for managing access of virtual machines.

One embodiment is directed toward a method for managing access ofvirtual machines executed by a host computer system to storage areanetworks. The method includes connecting, using the storage areanetworks, the host computer system with a storage system via switches,where the host computer system includes one or more host ports toconnect with a switch each, and where one or more port names areassigned to each virtual machine. The method also includes sending theport names of a virtual machine and a target port name as part of avalidate access command to the respective switch for each storage areanetwork connected with the host computer system. The method alsoincludes returning, by the switch, success information to the sendinghost computer system when receiving the validate access command by theswitch, in case all received virtual machine port names have access to atarget port assigned to the received target port name, otherwisereturning a fail information. The method also includes sending host portnames of the host computer system and logical unit names provided by thetarget port as part of the validate access command to the respectivetarget port, for each storage area network connected with the hostcomputer system and for each target port accessible by the storage areanetwork. The method also includes returning, by the storage system,success information to the sending host computer system when receivingthe validate access command by the target port, in case all receivedhost port names have access to logical units assigned to the receivedlogical unit name, otherwise returning a fail information.

Other embodiments are directed toward a system and computer programproduct for managing access of virtual machines

The above summary is not intended to describe each illustratedembodiment or every implementation of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings included in the present application are incorporated into,and form part of, the specification. They illustrate embodiments of thepresent disclosure and, along with the description, serve to explain theprinciples of the disclosure. The drawings are only illustrative ofcertain embodiments and do not limit the disclosure.

FIG. 1 depicts a configuration of a data processing system with storagearea networks (SANs) connecting host computer systems with storagesystems, according to various embodiments.

FIG. 2 depicts a flowchart for validating access of virtual machinesport names to target ports of the storage systems, according to variousembodiments.

FIG. 3 depicts a flowchart for validating access of host ports to logicunits of the storage systems, according to various embodiments.

FIG. 4 depicts a component diagram of the data processing system formanaging access of virtual machines executed by host computer systems toa storage area network, according to various embodiments.

FIG. 5 depicts an implementation chart according to the disclosed methodfor SAN access validation, according to various embodiments.

FIG. 6 depicts an implementation chart according to the disclosed methodfor target port access validation, according to various embodiments.

FIG. 7 depicts an example embodiment of a data processing system forexecuting a method, according to various embodiments.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION

Aspects of the present disclosure relate to data processing systems, andin particular, to a method, system and computer program product formanaging access of virtual machines executed by a host computer systemto storage area networks. While the present disclosure is notnecessarily limited to such applications, various aspects of thedisclosure may be appreciated through a discussion of various examplesusing this context.

The illustrative embodiments described herein provide a method, system,and computer program product for managing access of virtual machines tostorage area networks and storage systems. The illustrative embodimentsare sometimes described herein using particular technologies only as anexample for the clarity of the description. The illustrative embodimentsmay be used for managing access of virtual machines executed by a hostcomputer system to storage area networks, the storage area networksconnecting the host computer system with storage systems via switches.

FIG. 1 depicts a configuration of a data processing system 210 withstorage area networks (SANs) connecting host computer systems withstorage systems, according to various embodiments.

The data processing system 210 exhibits a number of virtual machines 10,12, 14, 16 running on two host computer systems 20, 22. These hostcomputer systems 20, 22 are connected via host ports 24, 25, 26, 27 withentry switches 34, 36 of two SANs 30, 32. Internally in the SANs 30, 32,the entry switches 34, 36 are routed via additional switches 38 forbeing connected with target ports 44, 45, 46, 47 of two storage systems40, 42. The storage systems 40, 42 are equipped with logical units(LUNs) 50, 51, 52, 53, 54. The virtual machines 10, 12, 14, 16 use apool of port names 18 for communicating with the SANs 30, 32 as well aswith the storage systems 40, 42.

The storage area networks 30, 32 may include fiber channel systems,whereas the virtual machine port names 18 may be implemented asworld-wide unique port names.

According to the embodiment of FIG. 1, a method for managing access ofthe virtual machines 10, 12, 14, 16 executed by the host computersystems 20, 22 to the storage area networks 30, 32 is described, wherethe storage area networks 30, 32 are connecting the host computersystems 20, 22 with the storage systems 40, 42 via switches 34, 36, 38,where the host computer systems 20, 22 includes one or more host ports24, 25, 26, 27 to connect with a switch 34, 36 each. The one or moreport names 18 are hereby assigned to each virtual machine 10, 12, 14,16. The disclosed method thus includes (i) for each storage area network30, 32 connected with the host computer system 20, 22 sending the portnames 18 of a virtual machine 10, 12, 14, 16 and a target port name 48as part of a validate access command to the respective switch 34, 36;and (ii) when receiving the validate access command by the switches 34,36, the switches 34, 36 are returning success information to the sendinghost computer system 20, 22 in case all received virtual machine portnames 18 have access to a target port 44, 45, 46, 47 assigned to thereceived target port name 48. Otherwise the switches 34, 36 arereturning a fail information. Secondly, the method includes, accordingto various embodiments, additionally or alternatively (iii) for eachstorage area network 30, 32 connected with the host computer systems 20,22 and for each target port 44, 45, 46, 47 accessible by the storagearea networks 30, 32 sending host port names 28 of the host computersystem 20, 22 and logical unit names 55 provided by the target port 44,45, 46, 47 as part of the validate access command to the respectivetarget port 44, 45, 46, 47; and (iv) when receiving the validate accesscommand by the target port 44, 45, 46, 47, the storage system 40, 42returning success information to the sending host computer system 20, 22in case all received host port names 28 have access to logical units 50,51, 52, 53, 54 assigned to the received logical unit name 55. Otherwisea fail information is returned, according to various embodiments.

The validate access command includes a set of target port names 48. Dueto the disclosed method the network access by one of the host ports 24,25, 26, 27 is established using a login in the respective switch 34, 36with a host port name 28 to which the switch 34, 36 responds withidentification data for the respective storage area network 30, 32,according to various embodiments. A fabric login may be performed viaeach host port 24, 25, 26, 27, the fabric login returning informationabout the storage area network 30, 32 being attached, the host port 24,25, 26, 27 currently not being logged in the storage area network 30,32.

A zone may be defined comprising the virtual machines port names 18 andthe target ports 44, 45, 46, 47 accessible for the virtual machine portnames 18. Further a group of logical units 50, 51, 52, 53, 54 of eachstorage system 40, 42 may be defined accessible via target ports 44, 45,46, 47 of the storage system 40, 42 for the virtual machine port names18.

FIG. 2 depicts a flowchart for validating access of virtual machinesport names to target ports of the storage systems, according to variousembodiments.

In FIGS. 2 and 3, reference numerals shown in FIG. 1 are also used.According to the disclosed method the program flow starts withparameters of the virtual machine port names 18 and the target portnames 48. In step S102 a list of zones for each port name 18 is created,according to various embodiments. Next in step S104 a response list witha row for each port name 18 and column for each target port 44, 45, 46,47 is created. Further in addition a summary list is established. Instep S106 for each target port name 48 the next target port name 48 isfetched. For each port name 18 the next port name 18 is fetched in stepS108. In step S110 it is checked if the same zone is part of the targetport zone list and the port zone list. If ‘yes’ in step S112 an ‘ok’ isentered in the response list entry for the target port 44, 45, 46, 47and the port name 18, otherwise, a ‘no’ is entered into the responselist. Then the flow continues with step S116 checking if this is thelast port name 18. If this was not the last port name 18 the loop isreentered with step S108, otherwise a next check is performed in stepS118 if the target port name 48 is in a zone with each port name 18. If‘yes’ the summary is updated in step S128 with ‘yes’, otherwise with‘no’ in step S120. The flow continues with check S122 if this was thelast target port name 48. If ‘yes’ the result is converted in step S124into an appropriate format according e.g. the extended link service(ELS) and the response list sent back in step S126, otherwise the loopis reentered in step S106, according to various embodiments.

FIG. 3 depicts a flowchart for validating access of host ports to logicunits of the storage systems, according to various embodiments.

The program flow according to the disclosed method starts with theparameters virtual machine port names 18 and the names of the logicalunits 50, 51, 52, 53, 54. In step S202 for each logical unit 50, 51, 52,53, 54 the name of the next logical unit is fetched and in step S204 foreach port name 18 the next port name 18 is fetched. In step S206 it ischecked if the port name 18 has access to the logical unit 50, 51, 52,53, 54 through a target port 44, 45, 46, 47. If ‘yes’ an ‘ok’ is enteredin the response list entry for the port name 18 in step S208, otherwisea ‘no’ is entered in step S210. Then the flow is continued with thecheck in step S212 if this was the last port name. If ‘yes’ the resultis converted in step S214 into an appropriate format according e.g. theextended link service (ELS) and the response list sent back in stepS216, otherwise the loop is reentered in step S204 for the next portname 18, according to various embodiments.

FIG. 4 depicts a component diagram of the data processing system 210 formanaging access of virtual machines executed by host computer systems toa storage area network, according to various embodiments. In FIG. 4reference numerals already shown in FIG. 1 are also used.

Access consistency validation according to the disclosed method isperformed by a validate access command via an access validation program64, that runs on a cluster management console 60 of a data processingsystem 210. The access validation requirements and results are recordedin access consistency groups 66, also maintained and persisted on thecluster management console 60, according to various embodiments. Theaccess validation program 64 accesses the nodes of the cluster via acluster management network 62.

One possible goal is to validate the consistency of the access group 66.This access consistency groups 66 consist of (a) virtual machine portnames 18 (b) target port names 48 and logical units 50, 51, 52, 53, 54(c) host ports 24, 25, 26, 27. Consistency is achieved, when each portname 18 can reach all logical units 50, 51, 52, 53, 54 through all ofthe host ports 24, 25, 26, 27. The access validation program 64determines the SAN 30 for each host port 24, 25, 26, 27. Further, itinitiates that the validate access consistency command is sent to eachSAN 30, and to each applicable storage subsystem target port 44, 45, 46,47, according to various embodiments. The structure of the accessconsistency group 66 and the steps of the validation are described inmore detail on the following charts in the FIGS. 5 and 6.

FIG. 5 depicts an implementation chart according to the disclosed methodfor SAN access validation, according to various embodiments.

A storage validation list 68 is defined comprising information from thevalidate access command. The storage validation list 68 includes anentry for each combination of a storage area network 30, 32, listed inthe access consistency group 66, and the group of logical units 56 for avalid access of a virtual machine port name 18 to the storage system 40,42.

The implementation of the disclosed method is started with an accessconsistency group 66 being created for one or more virtual machines 10,12, 14, 16, consisting of a set of virtual machines port names 18, thehost ports 24, 25, 26, 27 to be used and one or multiple LUN Groups,each referencing one or multiple LUN numbers, and the target port names48 which can be used to access the LUNs 50, 51, 52, 53, 54.

Variations of a consistency group 66 are possible. For example, withoutany target port 44/LUN 50 information, at the beginning of this processperforming discovery for one host port name per SAN 30, filling the SAN30/Target Port 44/LUN Group information based upon the gatheredinformation.

The port names 18 are recorded in a virtual machine port name list,according to various embodiments. A host port list is initialized withthe set of host ports 24, 25, 26, 27 that are part of this consistencygroup. A storage validation list 68 is initialized.

The SAN 30, 32 attached to each host port 24, 25, 26, 27 is determined.A fabric login is performed via each host port 24, 25, 26, 27, using oneof the port names 18, according to various embodiments. The fabric loginreturns the information which SAN 30, 32 is attached. If the SAN 30, 32is known already, no fabric login needs to be done. Fabric login isgenerally done with a port name 18, which is not currently logged in,according to various embodiments.

The validate access command is sent to each SAN 30, 32. Parameters arethe target port names 48 from the LUN groups and the virtual machineport names 18.

The storage validation list 68 is filled with the information returnedby the validate access command. If the summary for a target port says‘ok’, all virtual machines port names 18 have access to the target port44, 45, 46, 47. An entry is added to the storage validation list 68 tothe SAN 30, 32, concerning the SAN 30, 32, the target port 44, 45, 46,47, and the LUN group 56 from the LUN groups list.

Finally, an entry exists in the storage validation list 68 for each SAN30, 32, listed in the host port list and LUN group combination. If thisis not the case, some of the SANs 30, 32 don't allow access to some ofthe LUNs 50, 51, 52, 53, 54 and the access consistency group 66 isinconsistent. Optionally the SAN/LUN group combination which was notsuccessful in the SAN consistency column could be filled. The accessconsistency group 66 may be considered to be consistent if there is anentry for each combination of a SAN 30, 32 and a LUN group 56.

Alternatively, because a target port 44, 45, 46, 47 could be assigned toseveral LUN groups 56, an entry could be made for each SAN/targetport/LUN group combination with results of validate access commands.Then it would be checked if each SAN 30, 32 has access to each LUN group56.

FIG. 6 depicts an implementation chart according to the disclosed methodfor target port access validation, according to various embodiments.

A final SAN validate access consistency result table 69 is created. Thevalidate access command is sent to each target port 44, 45, 46, 47 inthe storage validation list 68, according to various embodiments.Multiple entries may exist, if the target port 44, 45, 46, 47 isreferenced by multiple LUN groups.

Parameters are the virtual machines port names 18 from the virtualmachine port name list and the LUNs 50, 51, 52, 53, 54 from the LUNgroup. The storage validation list is filled with the informationreturned by the validate access command. If all virtual machine portnames 18 have access to the LUNs 50, 51, 52, 53, 54 provided asparameters through the validate access command, an ‘ok’ is marked in thestorage subsystem consistency field for the target port 44/LUN groupcombination. It should be noted that it is sufficient to check the LUNsummary of the response. Otherwise, a ‘no’ is marked in the storagesubsystem consistency field for the target port 44/LUN groupcombination, according to various embodiments.

The access consistency group is consistent, if at least one entry existsin the storage validation list for each SAN/LUN group combination with‘ok’ in the SAN consistency field and ‘ok’ in the storage subsystemconsistency field.

FIG. 7 depicts an example embodiment of a data processing system 210 forexecuting a method, according to various embodiments.

Data processing system 210 is only one example of a suitable dataprocessing system and is not intended to suggest any limitation as tothe scope of use or functionality of embodiments of the inventiondescribed herein. Regardless, data processing system 210 is capable ofbeing implemented and/or performing any of the functionality set forthherein above.

In data processing system 210 there is a computer system/server 212,which is operational with numerous other general purpose or specialpurpose computing system environments or configurations. Examples ofwell-known computing systems, environments, and/or configurations thatmay be suitable for use with computer system/server 212 include, but arenot limited to, personal computer systems, server computer systems, thinclients, thick clients, handheld or laptop devices, multiprocessorsystems, microprocessor-based systems, set top boxes, programmableconsumer electronics, network PCs, minicomputer systems, mainframecomputer systems, and distributed cloud computing environments thatinclude any of the above systems or devices, and the like.

Computer system/server 212 may be described in the general context ofcomputer system executable instructions, such as program modules, beingexecuted by a computer system. Generally, program modules may includeroutines, programs, objects, components, logic, data structures, and soon that perform particular tasks or implement particular abstract datatypes. Computer system/server 212 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 7, computer system/server 212 in data processing system210 is shown in the form of a general-purpose computing device. Thecomponents of computer system/server 212 may include, but are notlimited to, one or more processors or processing units 216, a systemmemory 228, and a bus 218 that couples various system componentsincluding system memory 228 to processor 216.

Bus 218 represents one or more of any of several types of busstructures, including a memory bus or memory controller, a peripheralbus, an accelerated graphics port, and a processor or local bus usingany of a variety of bus architectures. By way of example, and notlimitation, such architectures include Industry Standard Architecture(ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA)bus, Video Electronics Standards Association (VESA) local bus, andPeripheral Component Interconnect (PCI) bus.

Computer system/server 212 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 212, and it includes both volatileand non-volatile media, removable and non-removable media.

System memory 228 can include computer system readable media in the formof volatile memory, such as random access memory (RAM) 230 and/or cachememory 232. Computer system/server 212 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 234 can be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 218 by one or more datamedia interfaces. As will be further depicted and described below,memory 228 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments of the invention.

Program/utility 240, having a set (at least one) of program modules 242,may be stored in memory 228 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment. Program modules 242 generally carry out the functionsand/or methodologies of embodiments of the invention as describedherein.

Computer system/server 212 may also communicate with one or moreexternal devices 214 such as a keyboard, a pointing device, a display224, etc.; one or more devices that enable a user to interact withcomputer system/server 212; and/or any devices (e.g., network card,modem, etc.) that enable computer system/server 212 to communicate withone or more other computing devices. Such communication can occur viaInput/Output (I/O) interfaces 222. Still yet, computer system/server 212can communicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via network adapter 220. As depicted, network adapter 220communicates with the other components of computer system/server 212 viabus 218. It should be understood that although not shown, other hardwareand/or software components could be used in conjunction with computersystem/server 212. Examples, include, but are not limited to: microcode,device drivers, redundant processing units, external disk drive arrays,RAID systems, tape drives, and data archival storage systems, etc.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may includecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein includes anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

In the drawings, like elements are referred to with equal referencenumerals. The drawings are merely schematic representations, notintended to portray specific parameters of the invention. Moreover, thedrawings are intended to depict only typical embodiments of theinvention and therefore should not be considered as limiting the scopeof the invention.

The descriptions of the various embodiments of the present disclosurehave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A method comprising: defining a storagevalidation list indicating at least that: for a first storage areanetwork connecting a host computer system to a storage system,respective virtual machines of a plurality of virtual machines executingon the host computer system have access to a first group of logicalunits via a first target port of the storage system; and for a secondstorage area network connecting the host computer system to the storagesystem, respective virtual machines of the plurality of virtual machinesexecuting on the host computer system have access to a second group oflogical units via a second target port of the storage system.
 2. Themethod according to claim 1, further comprising: returning, by arespective switch of a respective storage area network connecting thehost computer system with the storage system, success information to thehost computer system in response to a respective virtual machine portname having access to a target port associated with a target port namespecified in a validate access command.
 3. The method according to claim2, wherein a network access is established, by a host port, using alogin in the respective switch with a host port name to which therespective switch responds with identification data for the respectivestorage area network.
 4. The method according to claim 2, wherein thevalidate access command comprises at least one target port name.
 5. Themethod according to claim 2, wherein the validate access command isperformed via an access validation program executing on a clustermanagement console of a data processing system.
 6. The method accordingto claim 5, wherein accessing nodes of a cluster by the accessvalidation program is performed via a cluster management network.
 7. Themethod according to claim 5, wherein the access validation program isconfigured to determine the storage area networks for respective hostports.
 8. The method according to claim 1, wherein the storagevalidation list contains an entry for respective combinations of storagearea network, target port, and logical unit group satisfying a storagearea network consistency and a storage system consistency.
 9. The methodaccording to claim 8, wherein a respective combination satisfies thestorage area network consistency when each virtual machine port name hasaccess to a given target port via a given storage area network.
 10. Themethod according to claim 8, wherein a respective combination satisfiesthe storage system consistency when, for a logical unit group, eachvirtual machine port name has access to each logical unit in the logicalunit group.
 11. The method according to claim 1, wherein the storagevalidation list is converted to an extended link service (ELS) format.12. The method according to claim 1, further comprising defining a zoneincluding at least one virtual machine port name and respective targetports accessible for the at least one virtual machine port name.
 13. Themethod according to claim 1, wherein logical units of the storage systemare accessible via target ports of the storage system for the virtualmachine port names.
 14. The method according to claim 1, furthercomprising defining an access consistency group including a set ofvirtual machine port names and host ports of the host computer system tobe used, and a group of logical units referencing respective targetports and logical units accessible via the respective target ports. 15.The method according to claim 14, wherein maintaining the accessconsistency group is performed on a cluster management console.
 16. Themethod according to claim 1, wherein the storage validation listincludes an entry for a combination of a storage area network, listed inan access consistency group, and a group of logical units for a validaccess of a virtual machine port name to the storage system.
 17. Acomputer program product comprising a computer readable storage mediumhaving program instructions embodied therewith, the program instructionsexecutable by a computer to cause the computer to perform a method,comprising: defining a storage validation list indicating at least that:for a first storage area network connecting a host computer system to astorage system, respective virtual machines of a plurality of virtualmachines executing on the host computer system have access to a firstgroup of logical units via a first target port of the storage system;and for a second storage area network connecting the host computersystem to the storage system, respective virtual machines of theplurality of virtual machines executing on the host computer system haveaccess to a second group of logical units via a second target port ofthe storage system.
 18. The computer program product according to claim17, the method further comprising: returning, by a respective switch ofa respective storage area network connecting the host computer systemwith the storage system, success information to the host computer systemin response to respective virtual machine port names having access to atarget port associated with a target port name specified in a validateaccess command.
 19. The computer program product of claim 17, whereinthe storage validation list contains an entry for respectivecombinations of storage area network, target port, and logical unitgroup satisfying a storage area network consistency and a storage systemconsistency.
 20. A system comprising: a processor; and a computerreadable storage medium for storing program instructions which, whenexecuted by the processor, perform a method comprising: defining astorage validation list indicating at least that: for a first storagearea network connecting a host computer system to a storage system,respective virtual machines of a plurality of virtual machines executingon the host computer system have access to a first group of logicalunits via a first target port of the storage system; and for a secondstorage area network connecting the host computer system to the storagesystem, respective virtual machines of the plurality of virtual machinesexecuting on the host computer system have access to a second group oflogical units via a second target port of the storage system.